You perform those in bulk, as a batch job when the client side pushes the state up when back online.

After all, if a client is offline, nothing they do can affect anyone else until they go back online.

And now one needs UI to show that all the forms one thought were saved are merely sent, and come back a "tasks" that still need user attention.

What was simple form validation is in "offline first" something akin to a mandatory content moderation step.